Hitherto, a silicon-containing pentacyclic compound represented by the formula: ##STR1## wherein R.sup.1 represents a monovalent group, and R.sup.2 and R.sup.3 each represent a divalent group; and a method for producing it, have not been known.
While the main chain of conventional polymers consists of a single strand, the main chain of ladder polymers consists of a double strand. Therefore ladder polymers have long been expected to be excellent in thermal-resistance, mechanical strength, and chemical resistance. Further, in recent years, conjugation-type ladder polymers have been given attention as electronic material and nonlinear optical material. However, there is difficulty in using conventional techniques to produce polymers having a complete ladder structure. Recently, although several methods that use Diels-Alder reaction or the like have been reported (e.g., Adv. Mater., 3, 282 (1991); and Macromolecules, 26, 5528 (1993)).